$\left(+4\right).\left(-5\right)+\left(-12\right)$

$\lim_{x\to0}\left(\frac{\cos\left(3x\right)-cos\left(5x\right)}{x^2}\right)$

$x\frac{dy}{dx}=\frac{x}{\cos\left(\frac{y}{x}\right)}+y$

$2\sin\left(x\right)+6=5$

$\frac{x^9\left(2x\right)^5}{x^2}$

$\frac{-2x}{5}+1<4$

$\int\frac{\left(x^3+1\right)}{sqrt\left(x^4+4x-3\right)}dx$